Squeeze film bearing support movement limiting apparatus

ABSTRACT

A shaft bearing assembly uses &#39;&#39;&#39;&#39;squeeze film action&#39;&#39;&#39;&#39; to damp vibrations in an annular bearing support member. To prevent the annular support member from rotating about its axis with the shaft but allow the freedom of movement in any radial direction necessary for the squeeze film action, a linking member has one end pivotally connected to the housing and the other pivotally connected to the annular support member near its outer edge. A thrust bearing between the housing and annular support member bears axial loads.

llnited States Patent [191 Davis SQUEEZE FILM BEARING SUPPORT MOVEMENTLIMITING APPARATUS Leonard C. Davis, Indianapolis, Ind.

General Motors Corporation, Detroit, Mich.

Dec. 15, 1972 Inventor:

Assignee:

Filed:

Appl. No.1

US. Cl. 308/174 Int. Cl. Fl6c 19/14 Field of Search 308/9, 122, 184,

References Cited UNITED STATES PATENTS 11/1968 Dee 308/9 Jan. 8, 1974Primary Exa'miner-Charles J. Myhre Assistant Examiner-F rank SuskoAtt0rney-Paul Fitzpatrick et al.

[57] ABSTRACT 3 Claims, 2 Drawing Figures SQUEEZlE FILM BEARING SUPPORTMOVEMENT LIMITING APPARATUS BACKGROUND OF THE INVENTION One effectiveapparatus for damping vibrations in a rotating shaft is a squeeze filmbearing support. The squeeze film bearing support comprises an annularsupport member for the outer race of the bearing assembly which has anannular outer surface that tits in a housing with a matching innersurface so that a thin annular gap exists between the two surfaces. Oneof the surfaces has formed therein a pair of grooves, each of whichcontains a ring which engages the other surface to enclose the annularspace between the housing and annular support member. A viscous liquidsuch as lubricating oil is forced into this annular space underpressure; and this liquid helps damp vibrations of the shaft and bearingassembly. In the prior art a plurality of somewhat flexible parallelarms arranged circularly in a squirrel cage configuration attach theannular support member to the housing. These arms prevent rotation ofthe annular support member, support axial loads, help support the shaftat rest or low speeds and allow design selection of some criticalspeeds; and, in addition, they are flexible enough to allow the movementin a radial direction necessary for squeeze film action. However, thesquirrel cage is expensive to manufacture ane assemble; and the partsare subject to failure through fatigue.

My invention performs the function of the squirrel cage at a lower cost.The annular support member is attached to the housing and prevented fromrotating with the shaft by a single linking member which preferably hasone end pivotally connected to the housing and the other end pivotallyconnected to the annular support member. A thrust bearing assembly isused'in conjunction with the linking member to absorb axial loads; andwave washers may be used with the rings to adjust critical speeds todesired values and help center the shaft at low speeds where squeezefilm action is not effective. Further details and objects of myinvention will be apparent in the following drawings and specification.

SUMMARY OF THE DRAWINGS FIG. 1 shows a cutaway view of my invention inits environment.

FIG. 2 is a sectional view along line 2-2 of FIG. 1.

Referring to FIG. 1, a shaft 2, which might be part of a gas turbineengine, is supported in a housing 4 on a bearing assembly 6, whichcomprises an inner member or race 8, a plurality of rolling members andan outer member or race 12. The inner race 8 is fixed to the shaft 2 forrotation therewith; and the outer race 12 is attached to an annularbearing support member 14. The annular bearing support member 14 has anannular outer surface 16, cylindrical in this embodiment, butpotentially of any smooth cross sectional shape, which outer surface 16has a diameter slightly smaller than that ofa matching inner annularsurface 18 of the housing 4. The annular bearing support member 14 has apair of grooves 20 breaking its outer surface 16; and in each of thegrooves 20 is a sealing ring 22, similar to a piston ring used in areciprocating piston engine, which may be biased radially outward by'aspring member such as wave washer 24. The sealing rings 22 engage thecylindrical inner surface 18 of the housing 4 to create an annular space26. The grooves 20 and rings 22 could also be placed in the innersurface 18 of the housing 4, if desired, to create the same annularspace 26. An oil supply channel 28, formed in the housing 4, connectsthe annular space 26 with fluid supply means, not shown. A viscousfluid, such as oil, is pumped by the fluid supply means through thechannel 28 into the annular space 26 under a preselected pressure. Eachof the sealing rings 22 has a gap 30, generally between 0.005 and 0.015inch wide, which allows the escape of enough heated lubricant from theannular space 26 to help cool the apparatus surrounding the annularspace 26. However, the rings 22 retain enough fluid so that the pressureof the fluid within the annular space 26 can be maintained between 30and psi.

When the shaft 2 is still or rotating slowly, its weight and that of thebearing assembly 6 and annular support member 14 is born by the rings 22and wave washers 24, if present. As the rotational speed of the shaft 2increases, rotational imbalances cause the axis of the shaft to rotateslightly about the axis of the inner surface 18 of the housing 4. Theshaft 2 causes the annular support member 14 to perform this circularmotion and the surface 16 and 18 tend to squeeze together at a pointwhich describes a circular motion at the same frequency. The pressurizedfluid, however, squeezed between the surfaces 16 and 18, in what isknown as squeeze film action, forms a positive pressure wedge in frontof the rotating squeeze point which assists the rings 22 and wavewashers 24 in preventing the surfaces 16 and 18 from coming intocontact. With a fluid supply pressure of 30 psi or more, a negativepressure distribution is created behind the squeeze point. If theelemental pressures are summed around the annular support member 14, theradial components cancel and the tangential components form a net torquewhich resists whirl ane thereby damps rotational vibrations. To assurethe supply of fluid to both sides of the rotating squeeze point, annularchannels 21 axially inward of the rings 22 in the grooves 20 and anotherannular channel 29 intersecting the inner end of the oil supply channel28 are supplied in the annular bearing support member 14 and housing 4,respectively.

Since an annular bearing support member 14 which rolled around the innersurface 18 of the housing 4 would not create the desired squeeze filmaction and might, in addition, cause the sealing rings 22 to wear outthrough excessive rubbing against the inner surface 18 of the housing 4,it is necessary that the annular bearing support member 14 not rotatewith the shaft 2. Referring to FIG. 2, the linking member 32 ispivotally connected at one end to a pin 34 which projects from thehousing 4 with an axis parallel to that of the shaft 2. Near its otherend, the linking member 32 is pivotally connected to a pin 36 whichprojects from a radial extension 38 of the annular bearing supportmember 14 with an axis parallel to that of the shaft 2. Thus, rotationof the annular bearing support member 14 and its sealing rings 22 abouttheir axes in the housing 4 is prevented; but translational motion ofthese parts in any radial direction, and therefore squeeze film action,is allowed.

The linking member 32 shown in this embodiment is rigid and pivotallyconnected at both ends. If the shaft is only to rotate in one direction,a flexible linking member such as a steel cable could be used; and, ifso, one or both of its ends could be rigidly rather than pivotally held.

To absorb axial loads on the shaft 2, a thrust bearing assembly 40,comprising a plurality of rolling members 39 in a cage 41, is positionedaxially between the annular bearing support member 14 and the housing 4and is retained by a circular projecting ridge 42 of the annular bearingsupport member 14.

I claim:

1. Apparatus for limiting the movement of a squeeze film bearing supportmember in a housing, the squeeze film bearing support member and housinghaving corresponding annular inner and outer surfaces. respectively,with axially spaced sealing rings positioned therebetween to form anannular space for the retention of fluid under pressure for the dampingof vibrations induced in the squeeze film bearing support member by abearing and rotating shaft supported therein, the apparatus comprising,in combination:

a linking member connected between the squeeze film bearing supportmember at a point radially outward of its axis and the housing to limitrotation of the squeeze film bearing support member, the linking memberbeing oriented in a plane generally perpendicular to said axis of thesqueeze film bearing support member;

and a thrust bearing between the squeeze film bearing support member andthe housing to support axial loads therebetween.

2. The apparatus of claim 1 in which the linking member is pivotallyconnected to the housing and squeeze film bearing support member formovement in its plane of orientation.

3. The apparatus of claim 2 additionally comprising spring members setin grooves in one of the annular surfaces to bias the rings against theother annular surface and further limit movement of the squeeze filmbearing support.

1. Apparatus for limiting the movement of a squeeze film bearing supportmember in a housing, the squeeze film bearing support member and housinghaving corresponding annular inner and outer surfaces, respectively,with axially spaced sealing rings positioned therebetween to form anannular space for the retention of fluid under pressure for the dampingof vibrations induced in the squeeze film bearing support member by abearing and rotating shaft supported therein, the apparatus comprising,in combination: a linking member connected between the squeeze filmbearing support member at a point radially outward of its axis and thehousing to limit rotation of the squeeze film bearing support member,the linking member being oriented in a plane generally perpendicular tosaid axis of the squeeze film bearing support member; and a thrustbearing between the squeeze film bearing support member and the housingto support axial loads therebetween.
 2. The apparatus of claim 1 inwhich the linking member is pivotally connected to the housing andsqueeze film bearing support member for movement in its plane oforientation.
 3. The apparatus of claim 2 additionally comprising springmembers set in grooves in one of the annular surfaces to bias the ringsagainst the other annular surface and further limit movement of thesqueeze film bearing support.